function ajax_tool(method,url,data){
    return new Promise(function(resolve,reject){
     let xhr = new XMLHttpRequest()
     if(method == "GET"){
         let newUrl = url + '?'
         for(let key in data){
             newUrl += `${key}=${data[key]}&`
         }
         newUrl = newUrl.slice(0,-1)
         xhr.open(method,newUrl)
         xhr.send()
     }else{
         let postData = ""
         for(let key in data){
             postData += `${key}=${data[key]}&`
         }
         postData = postData.slice(0,-1)
         xhr.open(method,url)
         xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded')
         xhr.send(postData)
     }
     xhr.addEventListener('readystatechange',function(){
         if(xhr.readyState == 4){
             if(xhr.status === 200){
                 resolve(JSON.parse(xhr.responseText))
             }else{
                 reject('请求失败了，请检查参数或地址是否有误')
             }
         }
     })
 
     })

   }

export {ajax_tool}